Flat no-leads packages such as QFN (quad-flat no-leads) and DFN (dual-flat no-leads) are used to physically and electrically connect integrated circuits to printed circuit boards. Two types of flat no-leads packages are common: cavity (i.e. with a cavity designed into the package containing air or nitrogen), and plastic-molded (i.e. with minimal air in the package).
Cavity packages are small and lightweight, with good thermal and electrical performance that makes them suitable for portable communication/consumer products. Applications include cellular phones, PDAs, wireless transmitters, RF front end, HD devices, microcontrollers, pre-amplifiers, servers, smart power suppliers, switches, DSPs, ASICs, MEMS (Micro Mechanical and Electrical System) and wrist watches.
Cavity packages are usually made up of three parts; a copper leadframe, plastic-molded body (open, and not sealed), and a cap or lid attached to the plastic portion of the leadframe. An integrated circuit is mounted to a die attach pad within the cavity, with wire leads connecting the IC to the leadframe. The leadframe terminates in contacts on the bottom of the package for providing electrical interconnection with a printed circuit board.
In conventional cavity packages, a two-metal layer organic laminate is used with a via connecting the top metal layer to the bottom metal layer in order to fabricate an isolated ring.